In the manufacture of patterned devices, such as semiconductor chips and chip carriers, the processes of etching different layers which constitute the finished product are among the most crucial steps involved. One method widely employed in the etching process is to overlay the surface to be etched with a suitable mask and then to immerse the substrate and mask in a chemical solution which attacks the substrate to be etched while leaving the mask intact. These wet chemical processes suffer from the difficulty of achieving well-defined edges on the etched surfaces. This is due to the chemicals undercutting the mask and the formation of an isotropic image. In other words, conventional chemical wet processes do not provide the selectivity of direction (anisotropy) considered necessary to achieve optimum dimensional consistent with current processing requirements.
Moreover, such wet etching processes are undesirable because of the environmental and safety concerns associated therewith. Often the solvents suggested are toxic; thereby creating disposal problems.
Accordingly, various so-called "dry processes" have been suggested to improve the process from an environmental viewpoint, as well as to reduce the relative cost of the etching. Furthermore, these "dry processes" have the potential advantage of greater process control and higher aspect ratio images.
Such "dry processes" generally involve passing a gas through a container and creating a plasma in this gas. The species in this gas are then used to etch a substrate placed in the chamber or container. Typical examples of such "dry processes" are plasma etching, sputter etching, and reactive ion etching.
Reactive ion etching provides well-defined, vertically etched sidewalls. A particular reactive ion etching process is disclosed, for example, in U.S. Pat. No. 4,283,249 to Ephrath, disclosure of which is incorporated herein by reference.
One problem associated with "dry processing" techniques is providing a patternable material which is sensitive to imaging radiation while, at the same time, being sufficiently resistant to the dry etching environment. In many instances, resistance to the dry etching, such as to the plasma etching active species, results in erosion of the mask material and the loss of resolution that had been generated by the lithographic exposure to the imaging radiation.
This is true for both positive organic resist materials and negative organic resist materials. A positive resist material is one which on exposure to imaging radiation is capable of being rendered soluble in a solvent in which the unexposed resist is not soluble. A negative resist material is one which is capable of polymerizing and/or insolubilizing upon exposure to imaging radiation.
One type of positive photosensitive material is based upon phenol-formaldehyde novolak polymers. A particular example of such is Shipley AZ1350 which is a m-cresol formaldehyde novolak polymer composition. Such is a positive resist composition and includes therein a diazoketone such as 2-diazo-1-naphthol-5-sulphonic acid ester. In such a composition the diazoketone, during the photochemical reaction, is converted to a carboxylic acid. This, in turn, renders the exposed resist film readily soluble in weakly alkali aqueous developer solvents. The composition usually contains about 15%, or so, by weight of the diazoketone compound.
A discussion of various photoresist materials can be found, for instance, in the Journal of the Electrochemical Society, Vol. 125, No. 3, March 1980, Deckert, et al., "Microlithography-Key to Solid-State Fabrication", pp. 45C-56C, disclosure of which is incorporated herein by reference.
In addition, certain siloxanes have been suggested as reactive ion etch barriers. For instance, see Fried, et al., IBM, Journal Research Development, Vol. 26, No. 8, pp. 362-371. Also, certain siloxanes have been suggested as e-beam sensitive resists. For instance, see Roberts, Journal of Electrochemical Society, Vol. 120, p. 1726, 1973; Roberts, Phillips Technical Review, Vol. 35, pp. 41-52, 1975; and Gazard, et al., Applied Polymer Symposium, No. 23, pp. 106-107, 1974.
Moreover, there have been suggestions that certain siloxanes, when imaged with electron beam (see Hatzakis, et al., Processing Microcircuit Engineering (Lausanne), p. 396, September 1981); and deep U.V. at about 2537 Angstrom (see Shaw, et al., SPE Photopolymer Conference, November 1982) act as an etch mask for an underlying polymer layer in an oxygen plasma.
U.S. Pat. No. 4,603,195 to Babich, et al. discloses materials which are resistant to dry-processing techniques and especially to reactive ion etching in oxygen plasma while, at the same time, capable of providing high resolution images. The compositions disclosed therein are obtained by interreacting a quinone diazo compound and an organosilicon compound.
In addition, examples of some dry-developable resists are provided in U.S. Pat. Nos. 4,426,247 to Tamamura, et al.; 4,433,044 to Meyer, et al.; 4,357,369 to Kilichowski, et al.; 4,430,153 to Gleason, et al.; 4,307,178 to Kaplan, et al.; 4,389,482 to Bargon, et al.; and 4,396,704 to Taylor. In addition, German patent application OS32 15082 (English language counterpart British patent application 2097143) suggests a process for obtaining negative tone plasma resist images. Such is concerned with a process involving entrapment of a silicon-containing monomer into a host film at the time of exposure to radiation and requires a processing step to expel the unincorporated silicon monomer from the film before plasma developing of the relief image.
A more recent example of a plasma developable resist is described in U.S. Pat. No. 4,552,833 in which a method is provided for obtaining a resist which is stated to be radiation sensitive and oxygen plasma developable. Such process involves coating a substrate with a film of a polymer that contains a masked reactive functionality, imagewise exposing the film to radiation under conditions that cause unmasking of the reactive functionality in the exposed regions of the film, treating the exposed film with a reactive organometallic reagent, and then developing the relief image by treatment with an oxygen plasma. The specific organometallic reagents described therein are trimethylstannyl chloride, hexamethyldisilazane, and trimethylsilyl chloride.
In addition, a method of obtaining a two-layer resist by top imaging a single layer resist is described in U.S. patent application Ser. No. 679,527 (FI9-84046, assigned to the assignee of the present application) which employs a monofunctional organometallic reagent.
Moreover, U.S. Pat. No. 4,782,008 (assigned to the assignee of the present application) discloses oxygen plasma resistant materials obtained by reacting a polymeric material with a multifunctional organometallic material. The organometallic material contains at least two functional groups which are reacted with reactive groups of the polymeric material. The polymeric material contains reactive hydroxyl groups and/or reactive hydroxyl functional precursor groups. The disclosures of the above two U.S. patent applications are incorporated herein by reference.
A further disclosure of photosensitive compositions containing organosilicon compounds can be found in U.S. Pat. No. 4,693,960.
U.S. Pat. No. 4,481,279 describes a dry developable radiation sensitive composition based upon polymeric materials containing unsaturated hydrocarbon bonds (e.g.--polybutadiene, epoxy-containing polymers and cyclolinear polymers) and certain organosilicon compounds which upon e-beam irradiation form a reaction product in the exposed areas. The reaction product is intended to be removed by oxygen plasma thereby providing a positive tone pattern.
Report RJ 4834 by McDonald et al. is of general interest concerning negative tone oxygen plasma developable resist based upon the photogeneration of a reactive functionality within the resist film which reacts with an organometallic reagent.
Moreover, photopolymerizable compositions that contain an epoxy polymer and various radiation sensitive onium salts have been suggested. For instance, see U.S. Pat. Nos. 4,069,055; 4,175,972; 4,572,890; 4,593,052; and 4,624,912.